>>3522262ISO, and Exposure are relative to the scene.
For portrait photography you can start with selecting your aperture, do you want a blurry background or do you want everything in focus? (example: f1.8 blurry, f8 in focus); After you decided your aperture now you have to select you shutter speed and ISO, you want to keep your ISO as low as possible to avoid noise, but this is not always the case like when indoor shooting or low light photography.
so for example if you are using a 50mm f1.8, you want to keep your shutter speed over 1/50 to avoid camera shake, but this wont avoid motion blur, so if your subject blinks or move its head you will get motion blur.
A good way to start if you are new to using your camera is using Aperture Priority (A for Nikon, Av for Canon) which means you will pick your aperture and the camera will decide the shutter speed and ISO for you (this is good for portrait and non moving subjects)
Shutter speed priority (S for Nikon, Tv for Canon) is good for freezing action, so you will pick your shutter speed and the camera will decide the apeture and ISO for you.
about colours when shutting raw, it will all depend on the software you are using to edit your images, since the photo is a raw image the camera will no affect the colors of it. I personally use adobe lightroom and there is a dropdown menu to select color profile. on the 2 images that you share it looks like they were using "Flat, Neutral, or Portrait" profiles, since there is not a lot of saturation in the image.
Hope everything I said makes sense to you.
